[jira] [Created] (IMPALA-8095) Detailed expression cardinality tests

["Paul Rogers (JIRA)" <ji...@apache.org>]

Paul Rogers created IMPALA-8095:
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             Summary: Detailed expression cardinality tests
                 Key: IMPALA-8095
                 URL: https://issues.apache.org/jira/browse/IMPALA-8095
             Project: IMPALA
          Issue Type: Improvement
          Components: Frontend
    Affects Versions: Impala 3.1.0
            Reporter: Paul Rogers
            Assignee: Paul Rogers


Cardinality is a critical input to the query planning process, especially join planning. Impala has many high-level end-to-end tests that implicitly test cardinality at the "wholesale" level: A test will produce a wrong result if the cardinality is badly wrong.

But, at present, no detailed unit tests exist for this topic. This ticket asks to add tests for:

* Table cardinality, NDV values and null count in metadata retrieved from HMS.
* Table cardinality, NDV values and null counts in metadata presented to the query.
* Expression NDV and selectivity values (which derive from table cardinality and column NDV.)

Since none of the existing "functional" tables provide the level of detail needed for these tests, add a new test table specifically for this task.



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